Introductory/ Neuroimaging: What you need to know at 3 am And some cool stuff

1. Introductory Neuroimaging: What you need to know at 3 am And some cool stuff. . .

Kathleen Tozer, MD

2. Outline

• Choosing a study
• Normal anatomy
• Trauma
• Ischemic stroke
• Aneurysm

3. Outline

• Choosing a study
• Normal anatomy
• Trauma
• Ischemic stroke
• Aneurysm

4. Which study? Acute change

• For acute mental status change, first study is
ALWAYS noncontrast head CT
• Brain MR:
– Stroke protocol (noncontrast)
– ICH protocol (with contrast)
– Tumor protocol (with contrast)

5. Which study? Vascular

• CTA:
– Neck: Aortic arch through Circle of Willis.
– Head: Circle of Willis only
• MRA:
– Brain: noncontrast
– Neck: without and with contrast.

6. Regarding contrast:

• Iodinated contrast:
– GFR > 60:
• in the clear
– GFR < 60:
• If acute, tread cautiously, especially if <30
• Hydration, mucomyst, Sodium bicarb protocol
• Decrease dose, Visipaque
– ESRD:
• Coordinate with hemodialysis

7. Regarding contrast:

• Gadolinium contrast:
– GFR > 60:
• in the clear
– GFR 30-60:
• weigh risks.
• Consider noncontrast study first.
• Multihance
– GFR < 30:
• CONTRAINDICATED due to risk of NSF (nephrogenic systemic
fibrosis).
– Try noncontrast.
– Consult radiology for alternative studies.

8. Hounsfield Units (HU)

• CT density scale:
–
–
–
–
–
–
–
Air = -1000
Fat = -120
Water = 0
Muscle = +40
Blood clot = +65
Bone = +1000
Metal >> +1000

9. Outline

• Choosing a study
• Normal anatomy
• Trauma
• Ischemic stroke
• Aneurysm

10. Normal Anatomy

11. Normal Anatomy

12. Normal Anatomy

13. Normal Anatomy

14. Acute Head CT Checklist

Midline Shift
Mass Effect
Density
CSF Spaces
Vascular Territories
Intra-/Extra-axial
Herniation

15. Outline

• Choosing a study
• Normal anatomy
• Trauma
• Ischemic stroke
• Aneurysm

16.

17. Epidural Hematoma

• Injury to epidural vessel
– Arterial bleeding
• Lentiform shape
• Does not cross sutures
– May cross falx or tentorium
• Look for:
– FRACTURE
– RAPID EXPANSION

18.

19. Acute Subdural Hematoma

• Injury to bridging vessel
– Venous
• Crescent shaped
• May cross sutures
– Does not cross falx or
tentorium
• Does not enter sulci
• Watch for:
– MASS EFFECT
– SLOW EXPANSION

20.

21. Chronic Subdural Hematoma

• HYPODENSE
– (blood degradation)
• MIXED
– (Acute-on-chronic)

22.

23. Isodense Subdural Hematoma

• ISODENSE
– Coagulopathy
– Anemia
– Evolution of blood
products
• Look for:
– Sulcal Effacement
– Subtle Mass Effect

24.

25. Subarachnoid Hemorrhage

• Subarachnoid
– Sulci
– Cisterns
– Ventricles
• Trauma
– lateral convexities
• Aneurysm
– basal cisterns
• Interpeduncular Cistern
– most sensitive

26.

27. Cerebral Contusion

• Intraparenchymal
• “Coup-Contrecoup”
– Blow to head
– Sudden deceleration
– Brain impacts inner table
(contralateral side)
• Look for:
– Scalp contusion
– Halo of edema

28.

29. Subcortical Injury

• Shear-Strain forces
– Penetrating vessels
– Axonal injury
• “Tip of the iceberg”
– Consider MRI
• Neurological deficits may
be out of proportion to
degree of injury visible on
CT

30. MRI: Diffuse Axonal Injury

31.

32.

33. Diffuse Cerebral Edema

• Grey-white interface often
obscured
• Sulcal effacement
• Focal subtypes:
– Vasogenic
• Extracellular
• White matter > GM
– Cytotoxic
• Intracellular
• Grey matter > WM

34. Outline

• Choosing a study
• Normal anatomy
• Trauma
• Ischemic stroke
• Aneurysm

35. Stroke

36.

37. Acute Ischemia-Infarction

• Subtle HYPODENSITY
– Vascular distribution
– Loss of grey-white margin
• CT often NEGATIVE
• Early CT signs
– “Hyperdense MCA”
– “Insular ribbon”
• Role of CT: EXCLUDE
BLEED
• MRA or CTA useful
• DSA for intervention
• Early treatment may
improve outcome

38. Diffusion-MRI: Acute Infarct

39.

40. Acute facial droop, hemiparesis

41.

42.

CTA

43. Angio

44. Post intervention

45. Watershed Infarction

46.

47.

48.

15 hours
later

49. Anoxic brain injury

• Loss of Gray-White
• Progresses with
worsening edema
• PseudoSAH
• Hydrocephalus
• Cisterns
compressed

50. Subacute Infarction

2-14 days out
Hypodensity
ENHANCEMENT
Hemorrhagic
transformation

51. MRI: Enhancing Subacute Infarct

52. Chronic Infarction

• VOLUME LOSS
– Ex vacuo dilatation
• Hypodensity
– encephalomalacia

53. Dural Sinus Thrombosis

• Occlusive thrombosis
• Subtle early signs
– Bilateral infarcts
– Hemorrhages
• CTV or DSA
– Filling defect
• MRI/MRV

54.

55. Outline

• Choosing a study
• Normal anatomy
• Trauma
• Ischemic stroke
• Aneurysm

56.

57. Aneurysmal SAH

• Sudden severe headache
• HYPERDENSE CSF spaces
• Location
– Interhemispheric: ACoA
– Sylvian: MCA
• HYDROCEPHALUS,
VASOSPASM and
ISCHEMIA
– MUST find the aneurysm!
• DSA, CTA and/or MRA

58. Saccular Aneurysm

59. Fusiform Aneurysm

60. Active Re-bleeding

61. Ruptured Aneurysm

62.

63. Intracerebral Hemorrhage

• Hypertension
– Most common
– Characteristic Locations
• IF LOBAR BLEED:
– SEARCH for underlying
cause!
– MRI/MRA/MRV
– DSA or CTA
– Repeat imaging if negative
initially
• Look for:
– EXPANSION
– UNDERLYING LESION

64. MRI: Blood Products

65. MRI: Hemorrhagic Tumor

66.

67. Parenchymal Hemorrhage with Ventricular Extension

68. MRI Flow Voids: AVM